The present invention concerns an extension guide for drawers comprising a carcass rail to be fixed to a furniture carcass, a drawer rail to be fixed to the drawer and a central rail mounted movably between the carcass rail and the drawer rail. At least one running carriage is mounted displaceably between at least two rails of the extension guide, and a synchronization device for avoiding running faults of the extension guide is provided. The synchronization device has at least one synchronization wheel which co-operates on the one hand with the at least one running carriage and on the other hand with a running surface on one of the rails, and the synchronisation wheel is in the form of a gear having two pinion wheels of differing diameters.
The invention further concerns an article of furniture having at least one drawer which is mounted displaceably relative to a furniture carcass by way of an extension guide of the kind to be described.
In extension guides for drawers which are in the form of a full pull-out extension arrangement comprising a carcass rail, a drawer rail, and a central rail operative therebetween, a synchronization device is to be provided to avoid running faults in respect of the extension guide. Such running faults are both incorrect rail positions and also incorrect positions of the running carriage, which in normal use can lead to the drawer staying open. An incorrect rail position occurs, for example, if the drawer rail deviates from synchronous movement relative to the displaceable central rail, whereby the relative position of the rails in relation to each other is not correct. In contrast, running carriage faults denote incorrect positioning of the running carriage which builds up over an opening and closing movement and which are determined by the built-up difference in relation to the correct starting position. A fault of the running carriage can build up in particular due to slippage or because of elasticity in the rolling or running system during the operating movements. As from a given number of movements the carriage can be so far from its required position that it encounters an end-of-travel abutment in the rail system before the drawer is at all completely closed.
Extension guides frequently have a pull-in device with a damper which damps the pull-in movement of the drawer over the last closing range of movement of the drawer as far as the completely closed position. Those dampers, however, reduce the closing dynamics of the drawer in such a way that a running fault which has occurred during the movement of the drawer can no longer be compensated due to the lack of kinetic energy. In any additional movement in which the drawer is not completely opened, the drawer remains stopped in a further open position corresponding to the running fault, and that can be visually unattractive and also dangerous.
Numerous solutions have already been proposed for correcting or avoiding such incorrect movements of the rails and/or the running carriage. A running carriage synchronization arrangement is described, for example, in AT 360 699 B to the present applicant, wherein the running carriage which is mounted displaceably between the carcass rail and the central rail and the running carriage which is displaceable between the central rail and the drawer rail are positively controlled relative to each other by way of a gear mounted to the central rail.
A rail synchronization arrangement is described for example in AT 388 855 B, wherein the operating movements of the rails are controlled by way of a gear in engagement with tooth portions arranged on the rails.
EP 1 374 734 A proposes a drawer guide which has both a synchronization device for synchronization of the carriages and also an additional compensation device for compensating a synchronous running fault in respect of the rails.
DE 10 2005 016 418 A1 discloses a drawer extension guide having a synchronization device, wherein the synchronization wheel has two pinion wheels of differing diameters. The smaller pinion wheel controls the movement of the drawer rail relative to the carcass rail while the larger pinion wheel always controls the movement between two carriages which run between different pairs of rails. The two pinion wheels are mounted on a common shaft, but they run separately and independently of each other so that there is no synchronization between the two pinion wheels.